The present invention relates to a stroker. The invention relates more particularly to a stroker for use in a borehole in the ground, the stroker at least comprising an actuator arranged for being able to displace a tool in the longitudinal direction of the borehole, and grippers arranged to anchor the stroker to the wall of the borehole, alternatively to a pipe wall.
The English term stroker is used in the original description as the term is common in the petroleum industry.
During downhole work operations, especially in so-called deviated wells, it is common practice to connect a wireline tractor to a stroker to enable displacement of the stroker to the work location.
A stroker is typically four to six meters long, while a wireline tractor is generally about five to seven meters long. The overall length can therefore be up to thirteen meters, which might lead to sluicing problems at the surface valve and complicate downhole operations.
A further disadvantage with prior art stroker-wireline tractors is that the control system for one of the units must be switched off in order to operate the other. This is because the two machines utilize the same cables in the wireline for power supply and control. It is known that this lack of simultaneous control, due to gravitation and forces from fluid flowing in the borehole, may result in displacement of the wireline tractor during the time span between disconnection of the wireline tractor's control system and the anchoring of the stroker, which might cause failure of the downhole work operation.